System and methodology for pressure compensation

ABSTRACT

A technique facilitates pressure compensation with respect to a tool while also limiting detrimental influx of contaminants. A pressure compensation mechanism comprises a fluid trap chamber which is in fluid communication with a clean fluid chamber via a connector passage. The fluid trap chamber also is in communication with an external pressure region via an inlet passage. The connector passage is located such that a potentially contaminating fluid, e.g. water, entering via the inlet passage is isolated from the clean fluid chamber. The connector passage remains isolated regardless of whether the pressure compensation mechanism is in a vertical operational position or a deviated operational position.

BACKGROUND

In many hydrocarbon well applications, a wellbore is drilled into a desired hydrocarbon-bearing formation. Well tools are deployed downhole into the wellbore and pressure differentials may be established between internal regions and external regions along certain well tools. Some well tools are constructed with components which operate in a clean fluid, e.g. oil, held within a reservoir of a corresponding housing unit. Such housing units are constructed to maintain a positive pressure in the oil reservoir which drives oil through an elastomeric seal and outwardly into the surrounding environment. For example, the internal oil may be driven outwardly through the seal and into drilling fluid to exclude drilling fluid and particulate contaminants from the inside of the housing unit. The housing units tend to be bulky and expensive units which involve substantial maintenance before running the corresponding well tool downhole. Additionally, the finite supply of clean oil in the reservoir can limit the duration of a given job. The elastomeric seal or seals also are susceptible to failure and can limit the service temperature of the tool.

SUMMARY

In general, a system and methodology are provided to facilitate pressure compensation with respect to a tool while limiting detrimental influx of contaminants. In an embodiment, a pressure compensation mechanism comprises a fluid trap chamber which is in fluid communication with a clean fluid chamber via a connector passage. The fluid trap chamber also is in communication with an external pressure region via an inlet passage. The connector passage is located such that a potentially contaminating fluid, e.g. water, entering via the inlet passage is isolated from the clean fluid chamber. The connector passage remains isolated from the potentially contaminating fluid regardless of whether the pressure compensation mechanism is in a vertical operational position or a deviated operational position.

However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

FIG. 1 is a schematic view of an example of a well system having a well string deployed in a wellbore, according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional view of an example of a pressure compensation assembly that may be used in the well string, according to an embodiment of the disclosure;

FIG. 3 is a cross-sectional view of an example of a pressure compensation assembly that may be used in the well string, according to an embodiment of the disclosure;

FIG. 4 is a cross-sectional view of an example of a pressure compensation assembly that may be used in the well string, according to an embodiment of the disclosure;

FIG. 5 is a cross-sectional view of an example of a pressure compensation assembly that may be used in the well string, according to an embodiment of the disclosure;

FIG. 6 is a cross-sectional view of an example of a pressure compensation assembly that may be used in the well string, according to an embodiment of the disclosure; and

FIG. 7 is a cross-sectional view of an example of a pressure compensation assembly that may be used in the well string, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

With respect to certain embodiments of the present disclosure, a system and methodology are provided to facilitate pressure compensation with respect to a tool while limiting detrimental influx of contaminants. For example, a pressure compensation mechanism may be employed to balance pressure and to prevent detrimental influx of water and/or particulates. In an embodiment, the pressure compensation mechanism comprises a fluid trap chamber which is in fluid communication with a clean fluid chamber via a connector passage. The clean fluid chamber may be in the form of an oil chamber containing a tool mechanism which operates in oil. For example, a variety of actuator mechanisms, bearing elements, or other tool mechanisms may be operated in an oil or other type of clean fluid.

In this example, the fluid trap chamber also is in communication with an external pressure region via an inlet passage. The connector passage is located such that a potentially contaminating fluid, e.g. water, entering via the inlet passage is isolated from the clean fluid chamber. The connector passage remains isolated from the potentially contaminating fluid regardless of whether the pressure compensation mechanism is in a vertical operational position or a deviated, e.g. horizontal, operational position. In many applications, the potentially contaminating fluid is heavier than the oil or other clean fluid. In some well applications, for example, the clean fluid comprises oil and the potentially contaminating fluid comprises water which may enter the wellbore from a surrounding formation or from other sources. The oil floats on water and this characteristic may be used to prevent the water from contaminating the oil chamber in which a given tool mechanism, e.g. bearing element or actuator, is operated.

For a variety of applications, the pressure compensation mechanism presents a simple technique and device for providing pressure compensation within housings containing mechanisms which run in a clean fluid, such as oil. The pressure compensation mechanism enables operation of such tool mechanisms without using conventional, expensive pressure housings and complex positive pressure oil chambers which utilize leaking oil.

Referring generally to FIG. 1, an example of a well system 20 is illustrated as having a well string 22, e.g. a tool string, deployed in a wellbore 24. The well string 22 comprises a conveyance 26 for delivering at least one tool 28 downhole into wellbore 24. Depending on the application, the conveyance 26 may comprise a cable, coiled tubing, production tubing, drilling tubing, or other suitable conveyances. In this example, tool 28 comprises a tool mechanism 30 which operates in clean fluid, e.g. oil. By way of example, the tool 28 may comprise a bearing and tool mechanism 30 may comprise a bearing element, e.g. a sleeve bearing element, roller bearing element, ball bearing element, or other suitable bearing element, which operates in oil or another suitable clean fluid. However, the tool mechanism 30 also may comprise a variety of tool actuators or other types of tool mechanisms which benefit from operation in oil or other types of clean fluid.

In this example, the tool 28 further comprises a pressure compensation mechanism 32. The pressure compensation mechanism 32 may be formed within a common housing of tool 28 or it may be constructed as a separate component operatively coupled with a main portion of tool 28. In this example, tool 28 comprises a well tool although the pressure compensation mechanism 32 may be used with a variety of other types of tools, including non-well type tools. The pressure compensation mechanism 32 balances pressure differentials between an internal region 34 of tool 28 and an external region 36. In a variety of well applications, the external region 36 may be a region within wellbore 24 but external to tool 28. Without the pressure compensation enabled by pressure compensation mechanism 32, the internal pressure of internal region 34 would remain at a differential with respect to the external pressure of external region 36. As described in greater detail below, the pressure compensation mechanism 32 also prevents contamination of a clean fluid chamber in which tool mechanism 30 operates.

Referring generally to FIG. 2, an example of pressure compensation mechanism 32 is illustrated. In this embodiment, the pressure compensation mechanism 32 comprises a housing 38 which extends to form a clean fluid chamber 40, e.g. oil chamber, in which tool mechanism 30 operates. The pressure compensation mechanism 32 further comprises a fluid trap chamber 42 which is in fluid communication with the clean fluid chamber 40 via a connector passage 44. The fluid trap chamber 42 also is in fluid communication with external pressure region 36 via an inlet passage 46.

The connector passage 44 may be located along a central axis 48 which intersects a center of the fluid trap chamber 32. In some embodiments, for example, the fluid trap chamber 42 is in the shape of a cylinder and the central axis 48 forms the main axis of the cylindrical shape of fluid trap chamber 42. Depending on the application, the pressure compensation mechanism 32 may comprise other features, such as a particle filter 50. Particle filter 50 is positioned to block flow of particles through the inlet passage 46.

As illustrated in FIG. 3, the clean fluid chamber 40, fluid trap chamber 42, connector passage 44 and inlet passage 46 may contain a clean fluid 52. In various applications, the clean fluid 52 comprises oil which, at least initially, fills the oil chamber 40 and fluid trap chamber 42. The connector passage 44 is located such that a potentially contaminating fluid heavier than the clean fluid 52, e.g. heavier than oil, which enters the fluid trap chamber 42 via inlet passage 46 collects in regions of the fluid trap chamber 42 which are separated from the connector passage 44. The fluid trap chamber 42 and the connector passage 44 are constructed and arranged so the potentially contaminating fluid remains separated from the connector passage 44 and thus outside of clean fluid chamber 40 regardless of whether the tool 28 is in a vertical operational position or a deviated, e.g. horizontal, operational position.

In the embodiment illustrated in FIG. 3, the inlet passage 46 is constructed as a simple tube 54. The particle filter 50 may be in the form of a fine mesh (or other suitable material) positioned over the end of the simple tube 54. The material used to form particle filter 50 may be selected to limit the passage of particles and also to limit outward leakage of clean fluid/oil 52 based on the viscosity of the clean fluid. In some applications, the particle filter 50 may be formed as a mesh cap and covered with a water-soluble plastic cap for transport purposes.

As illustrated in FIG. 4, potentially contaminating external fluid 56, e.g. water, can enter inlet passage 46 from a tool location exposed to the pressure of external region 36. In many applications, small volumes of external fluid 56 moving into inlet passage 46 are sufficient to equilibrate pressure between external region 36 and internal region 34 within clean fluid chamber 40. Effectively, the pressure differential between internal region 34 and external region 36 may be balanced or otherwise equilibrated via the pressure communication pathway formed along inlet passage 46, fluid trap chamber 42, and connector passage 44. In various types of well applications, the clean fluid 52 comprises oil and the potentially contaminating external fluid 56 comprises water.

In a variety of well applications, e.g. vertical wellbore drilling applications, the tool 28 remains in a vertical operational position in which fluid trap chamber 42 is below clean fluid/oil chamber 40, as illustrated in FIG. 4. In this orientation, the central axis 48 also is in a generally vertical orientation. One tool 28 is in this vertical operational orientation, the external fluid 56, e.g. water, remains within inlet passage 46 or within inlet passage 46 and a bottom region of fluid trap chamber 42. Thus, the potentially contaminating water or other external fluid 56 is separated from and maintained at a suitable distance from connector passage 44. Consequently, the water or other external fluid 56 is not able to enter the clean fluid chamber 40 containing tool mechanism 30.

However, the tool 28 also may be used in a deviated operational position in which the pressure compensation mechanism 32 is turned to a deviated, e.g. horizontal, operational position as illustrated in FIG. 5. Such an operational position may occur during, for example, horizontal wellbore drilling applications. In this orientation, the central axis 48 also is in a generally deviated, e.g. horizontal, orientation. When in the deviated operational position, the pressure differential between the internal pressure of internal region 34 and the external pressure at external region 36 may still equilibrate along the pathway formed by inlet passage 46, fluid trap chamber 42, and connector passage 44. However, external fluid 56, e.g. water, which enters through inlet passage 46 is collected along a lower side, e.g. a radially lower side, of fluid trap chamber 42, as illustrated in FIG. 6.

The configuration of fluid trap chamber 42 effectively traps the incoming external fluid 56 at a position separated from connector passage 44. Thus, the potentially contaminating fluid 56 is again prevented from entering the clean fluid/oil chamber 40 containing tool mechanism 30. It should be noted that in some applications, operation of the tool 28 may promote a mixing of the fluids and formation of some form of emulsion. However, the structure of fluid trap chamber 42 and connector passage 44 is still able to provide effective protection of clean fluid chamber 40.

The fluid trap chamber 42 may comprise a variety of shapes, however one useful shape is a cylindrical shape which facilitates collection and settling of incoming fluid 56 in a pool against an outer wall forming fluid trap chamber 42. The collection of incoming fluid 56 along an outer wall of fluid trap chamber 42 occurs regardless of the rotational orientation of pressure compensation mechanism 32 about axis 48. The cylindrical shape of the fluid trap chamber 42 also facilitates movement of the pool of fluid 56 along the outer wall surface of chamber 42 as the tool 28 and thus pressure compensation mechanism 32 rotate about axis 48. This configuration of fluid trap chamber 42 also minimizes mixing of external fluid 56 with clean fluid/oil 52. Because of the location of connection passage 44 (which may be in the form of a fine bore tube or other suitable form) there is no direct path by which the contaminant fluid 56 gains access to clean fluid chamber 40. Formation of connection passage 44 as a small diameter tube or other suitable, small passage further ensures limited space (or no space) for mixing of fluids in a manner which would allow the external fluid 56 access to clean fluid chamber 40.

Referring generally to FIG. 7, another embodiment of pressure compensation mechanism 32 is illustrated. In this embodiment, the fluid trap chamber 42 comprises a central region 58 separated from an outer region 60, e.g. an outer annular region by a baffle structure 62. Additionally, the baffle 62 may comprise a baffle member 64, e.g. a cross plate, positioned between inlet passage 46 and connector passage 44 within fluid trap chamber 42. By locating the cross plate 64 or other baffle member 64 between inlet passage 46 and connector passage 44, the progress of fluid 56, e.g. water, under shock accelerating conditions is hindered with respect to movement towards connector passage 44.

In some applications, the baffle 62 may be constructed to provide the central region 58 with a conical shape. The potentially contaminating external fluid 56 may be trapped in the outer annular region 60, at least when the pressure compensation mechanism 32 is in a deviated, e.g. horizontal, operational position as illustrated in FIG. 7. As with other embodiments described herein, the tool 28 and its pressure compensation mechanism 32 may be used in either vertical or horizontal operational positions while maintaining separation between external fluid 56 and clean fluid/oil chamber 40.

Depending on the application, the pressure compensation mechanism 32 can be used to equilibrate pressure and to guard against contamination in a variety of tools. In well applications, for example, the pressure compensation mechanism 32 may be employed to protect bearings, actuators, and/or other tool mechanisms in many types of downhole well tools. Similarly, the pressure compensation mechanism 32 may be used in drilling operations, production operations, injection operations, and/or other well related operations. However, the pressure compensation mechanism 32 also may be utilized in various non-well related applications with tools other than well tools.

The size and configuration of the pressure compensation mechanism 32 may be adjusted to accommodate the parameters of a given application. For example, the size and shape of the clean fluid chamber and the fluid trap chamber may be adjusted. Depending on the type of tool mechanism, e.g. bearing element or actuator, disposed in the clean fluid chamber, the shape and configuration of the interior wall surfaces defining the clean fluid chamber may be constructed accordingly. Similarly, the fluid trap chamber may have single regions or plural regions with cylindrical constructions, conical constructions, or other suitable constructions or combinations of differently shaped constructions. The clean fluid may comprise a variety of oils or other liquids suitable to downhole environments or other environments in which the pressure compensation mechanism is operated. Similarly, the diameter, length, and configuration of the connector passage and the inlet passage may be selected according to the parameters and goals of a given application.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 

1. A system for pressure compensation, comprising: a well string having a well tool with a tool mechanism which operates in oil contained within an oil chamber, the well tool further comprising: a pressure compensation mechanism having a fluid trap chamber in fluid communication with the oil chamber via a connector passage, the fluid trap chamber also being in communication with an external pressure region via an inlet passage, the connector passage being located such that fluids which enter the fluid trap chamber via the inlet passage and are heavier than the oil collect at regions of the fluid trap chamber separated from the connector passage regardless of whether the well tool is in a vertical operational position or a deviated operational position.
 2. The system as recited in claim 1, wherein the pressure compensation mechanism further comprises a particle filter positioned to block flow of particulates through the inlet passage.
 3. The system as recited in claim 1, wherein the fluid trap chamber is in the shape of a cylinder.
 4. The system as recited in claim 3, wherein the connector passage is in fluid communication with the fluid trap chamber at a central axis of the cylinder.
 5. The system as recited in claim 4, wherein the central axis is vertical when the well tool is in the vertical operational position.
 6. The system as recited in claim 4, wherein the central axis is horizontal when the well tool is in the deviated operational position and the deviated operational position is horizontal.
 7. The system as recited in claim 1, wherein the inlet passage places the fluid trap chamber in communication with external pressure within a wellbore along an exterior of the well tool.
 8. The system as recited in claim 1, wherein the fluid trap chamber comprises a central region separated from an outer annular region.
 9. The system as recited in claim 8, wherein the pressure compensation mechanism further comprises a baffle in the fluid trap chamber.
 10. A method for pressure compensation, comprising: positioning a tool mechanism of a tool in an oil chamber for operation in oil contained in the oil chamber; coupling the oil chamber with a fluid trap chamber via a connector passage; locating the connector passage such that water entering the fluid trap chamber does not reach the connector passage regardless of whether the tool is in a vertical operational position or a deviated operational position; and coupling the fluid trap chamber with an external region at an external pressure via an inlet passage to enable pressure compensation of the oil chamber via a pathway from the external region to the oil chamber along the inlet passage, the fluid trap chamber, and the connector passage.
 11. The method as recited in claim 10, further comprising preventing flow of particulates through the inlet passage via a particulate filter.
 12. The method as recited in claim 10, further comprising forming the fluid trap chamber as a cylinder.
 13. The method as recited in claim 12, further comprising joining the connector passage with the cylinder at a central axis of the cylinder.
 14. The method as recited in claim 10, further comprising forming the fluid trap chamber with a central region separated from an annular region.
 15. The method as recited in claim 14, wherein forming comprises forming the central region with a conical shape.
 16. The method as recited in claim 10, further comprising connecting the tool into a well string.
 17. The method as recited in claim 16, wherein coupling comprises compensating for a pressure differential between the oil chamber and a wellbore region external to the tool.
 18. A system, comprising: a pressure compensation mechanism having a fluid trap chamber, the fluid trap chamber being in fluid communication with a clean fluid chamber via a connector passage and with an external pressure region via an inlet passage, the connector passage being located such that water entering via the inlet passage is isolated from the clean fluid chamber when the pressure compensation mechanism is in a vertical operational position and when the pressure compensation mechanism is in a horizontal operational position; and a tool mechanism of a well tool, the tool mechanism being positioned for operation in the clean fluid chamber.
 19. (canceled)
 20. The system as recited in claim 19, wherein the connector passage, the fluid trap chamber, and the inlet passage form a pressure pathway between the clean fluid chamber and an external wellbore region. 